Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
  • B41M5/00—Duplicating or marking methods; Sheet materials for use therein
  • B41M5/124—Duplicating or marking methods; Sheet materials for use therein using pressure to make a masked colour visible, e.g. to make a coloured support visible, to create an opaque or transparent pattern, or to form colour by uniting colour-forming components
  • B41M5/165—Duplicating or marking methods; Sheet materials for use therein using pressure to make a masked colour visible, e.g. to make a coloured support visible, to create an opaque or transparent pattern, or to form colour by uniting colour-forming components characterised by the use of microcapsules; Special solvents for incorporating the ingredients
  • B41M5/1655—Solvents

Definitions

• This invention relates to an improved solvent for colour forming compounds (chromogens) for developers systems which are useful in the manufacture of carbonless copying paper.
• the most widely used form of carbonless copying paper comprises a two-sheet system in which the under surface of the top sheet has a coating of microcapsules of a solution of a colourless chromogen, while the upper surface of the lower (receiver) sheet has an absorbent coating including a sensitizing agent for the chromogen.
• a marking instrument is applied to the top sheet, the microcapsules are locally ruptured, thereby releasing the chromogen solution from the affected microcapsules to react with the underlying sensitizing agent and form coloured marks on the receiver sheet corresponding to the marks applied to the top sheet.
• the solvent for the chromogen is usually a mixture of a "primary solvent” which has higher solvency for the chromogen, with a cheaper diluent or "secondary solvent” such as kerosene.
• a primary solvent which has higher solvency for the chromogen
• secondary solvent such as kerosene
• a class of primary solvents which has already found wide application for use in carbonless copying paper manufacture are hydrogenated terphenyls. Although they have considerable merits, these solvents give with clay-coated receiver sheet systems rapid development of colour but moderate colour intensity, whereas with resin-coated receiver sheet systems, they give both relatively slow colour development and low colour intensity.
• the present invention is directed to improvements relating to another aspect of primary solvent performance in carbonless copying paper, namely the solvency power of primary solvents for the chromogen.
• the need for such improvements results from the desire to increase as far as possible the ratio of secondary to primary solvent, and the tendency in the industry to use new or improved chromogens which are more difficult to dissolve than some of those used previously.
• a primary solvent of the invention comprises a mixture of 80% to 5% wt of an aromatic, or a partially or fully hydrogenated aromatic hydrocarbon compound and 20% to 95% wt of an ether compound, and optionally is used in combination with a secondary solvent in a weight ratio primary : secondary solvent ranging from 95:5 to 20:80.
• a preferred primary solvent of the invention comprises as hydrocarbon compound an unsubstituted or substituted phenyl, biphenyl, terphenyl, naphthalene or diphenyl alkane derivative, or an unsubstituted or substituted partially or fully hydrogenated phenyl, biphenyl, terphenyl, naphthalene or diphenyl alkane derivative.
• the substituents in the substituted aromatic and partially or fully hydrogenated aromatic hydrocarbon compounds are preferably one or more hydrocarbon radicals independently selected from C1 - C20 alkyl, C3-C10 cycloalkyl, and aryl-C1-C6 alkyl wherein aryl means a phenyl or naphthyl or partially hydrogenated phenyl or naphthyl group optionally substituted with one or more C1-C8 alkyl radicals and/or C3-C10 cycloalkyl-C1-C6 alkyl radicals.
• Typical examples of commercially available hydrocarbon compounds useful in primary solvents of the invention are, for example, biphenyl, 1,2,3,4-tetrahydronaphthalene, decahydronaphthalene, monoisopropyl biphenyl, diisopropyl biphenyl, sec.butyl biphenyl, terphenyl , diphenyl methane, 1,1-diphenyl ethane, 1,2-diphenyl ethane, partially hydrogenated terphenyls, hexahydroterphenyls, dodecahydroterphenyls, diisopropylnaphthalene and styrenated tetralin.
• Preferred commercially available hydrogenated terphenyls include Santosol 340® and Santosol 300®, which are terphenyls partially hydrogenated to different extents, the latter having a higher degree of residual aromaticity than the former. (® Registered trade mark of Monsanto Company)
• the hydrocarbon compound of the primary solvent of the invention can be one single hydrocarbon derivative as defined above as well as a mixture in various proportions of the above defined hydrocarbon compounds.
• the ether compound of the primary solvent of the invention can be an aromatic ether or a di(arylalkyl)ether, as described in GB 1.517.647 and GB 1.564.931, respectively.
• Aromatic ethers which can be used in the solvents of the invention include di(aromatic) ethers, aliphatic (and cycloaliphatic) aromatic ethers, and (aromatic substituted aliphatic) aromatic ethers.
• An aromatic radical in an aromatic ether can be, for example, an aryl group, which contains from 6 to 14 ring carbon atoms, which is optionally substituted by one or more substituents independently selected from, for example, alkyl groups, (usually alkyl groups of 1 to 8 carbon atoms) and halogen atoms, for example chlorine and bromine.
• substituents independently selected from, for example, alkyl groups, (usually alkyl groups of 1 to 8 carbon atoms) and halogen atoms, for example chlorine and bromine.
• Examples of aryl and substituted aryl groups thus include phenyl, tolyl, chlorophenyl, naphthyl, ethylnaphthyl, and bromonap
• An aliphatic group can be for example an alkyl or alkenyl group, particularly an alkyl or alkenyl group of up to 8 carbon atoms, and which may, for instance, carry one or more halogen atoms as substituents. Examples are methyl, isopropyl, n-butyl, allyl, 2-ethylhexyl and chloroethyl. Cycloaliphatic groups include cycloalkyl and alkylcycloalkyl groups, and usually have 5 or 6 ring carbon atoms and a total of up to 10 carbon atoms. Examples are cyclopentyl, cyclohexyl and methylcyclohexyl.
• Aromatic substituted aliphatic groups are generally phenylalkyl or substituted phenylalkyl groups wherein the alkyl group contains for instance up to 6 carbon atoms and the substitution comprises one or more radicals independently selected from a C1-C8 alkyl group and/or a halogen atom. Examples are benzyl, alpha-methylbenzyl, alpha,alpha-dimethylbenzyl and o-chlorobenzyl.
• aromatic ethers thus include diaryl ethers, for example diphenyl ether and ditolyl ethers, alkenyl aryl ethers, for example allyl phenyl ether, alkyl aryl ethers, for example isobutyl phenyl ether, n-hexyl phenyl ether and 2-ethylhexyl phenyl ether, and aralkyl aryl ethers.
• diaryl ethers for example diphenyl ether and ditolyl ethers
• alkenyl aryl ethers for example allyl phenyl ether
• alkyl aryl ethers for example isobutyl phenyl ether, n-hexyl phenyl ether and 2-ethylhexyl phenyl ether
• aralkyl aryl ethers for example isobutyl phenyl ether, n-hexyl
• benzyl aryl ethers are a preferred class of aromatic ethers for use in the present invention.
• solvents as chromogen solvents in carbonless copying paper systems is described in British Patent Specification 1,434,495.
• Preferred ethers include phenyl benzyl ether, isopropylphenyl benzyl ether, ethylphenyl benzyl ether, tolyl benzyl ether, xylyl benzyl ether, tolyl alpha-methylbenzyl ether, tolyl 3-methylbenzyl ether and tolyl alpha,alpha-dimethylbenzyl ether.
• Di (arylalkyl) ethers useful in primary solvents of the invention are those of the formula wherein each R represents hydrogen, an alkyl group or a cycloalkyl group, each R' represents an alkyl group or a halogen atom, each n is an integer of from 1 to 6 and each m is 0 or an integer of from 1 to 5, and each R' m --(Ar)-- represents an aryl group when m is 0 or an alkyl- and/or halogen-substituted aryl group when m is a said integer.
• Each R m '--(Ar)-- can, for example, be an unsubstituted or alkyl- and/or halogen-substituted phenyl , naphthyl or biphenyl group.
• Each symbol R, Ar, R' , n and m can have a value which is the same as or different from that or those of the other symbols R, Ar, R' , n and m respectively in the formula.
• Preferred di(arylalkyl) ethers for use in the present invention are those wherein the total number of carbon atoms in the two groups does not exceed the total number of carbon atoms in the two Ar nuclei. Further features of preferred di(arylalkyl)ethers are that each R is hydrogen or an alkyl group of from 1 to 6 carbon atoms, especially a methyl group, and that if R represents a cycloalkyl group, this is a cyclohexyl group.
• R' in the above formula is preferably an alkyl group of from 1 to 12 carbon atoms, more especially an alkyl group of from 1 to 4 carbon atoms, for example methyl, ethyl, isopropyl or t-butyl.
• each m is 0 or has a value such that the total number of carbon atoms in R m ' does not exceed 6.
• R m ' represents an unsubstituted or alkyl substituted phenyl, naphthyl or biphenyl group, for example, a phenyl, tolyl, xylyl, ethylphenyl , naphthyl, methylnaphthyl , isopropylnaphthyl biphenyl or t-butyl-biphenyl radical.
• R' is preferably chlorine, such that ---(Ar)---R m ' may represent, for example, a chlorophenyl radical.
• preferred di(arylalkyl)-ethers for use in the present invention are those in which each n has the value 1 or 2.
• di(arylalkyl)ethers within the above formula are: dibenzyl ether, benzyl alpha-methylbenzyl ether, di(alpha-methylbenzyl)ether, di(alpha-ethylbenzyl)ether, di(alpha, alpha-dimethylbenzyl)ether, di(4- methylbenzyl)-ether, benzyl alpha-naphthylmethyl ether, benzyl beta-phenethyl ether and di(4-phenyl-n-butyl)-ether.
• a specific example of a polyphenyl ether is diphenoxybenzene.
• ethers for primary solvents of the invention are dibenzylether, ditolyl ether, benzyl phenyl ether and diphenoxybenzene.
• the ether compound of the primary solvent of the invention can comprise one single ether derivative or can include a mixture in various proportions of the ether compounds defined herein before.
• Mixtures that are liquids at room temperature may be used alone or in combination with secondary solvents, i.e. diluents.
• Mixtures which are solids or semisolids at room temperature are used in combination with a diluent in order to provide a solvent having the requisite degree of liquidity for use in carbonless copying paper systems.
• the diluent is usually an inert liquid miscible in all proportions with the hydrocarbon - ether mixture.
• suitable diluents include mineral and vegetable oils, such as kerosene, paraffin oil, castor oil, soyabean oil, and corn oil and alkylated benzenes.
• a particularly preferred diluent is kerosene.
• diluents function to alter physical properties of the solvent such as viscosity or vapour pressure as may be desired for improved handling or processing.
• solvents of the invention may also be mixed with other compounds which are not merely diluents, but are themselves active in the sense of enhancing the speed or intensity of print development in carbonless copying paper systems.
• Such compounds generally have at least one aromatic nucleus in the molecular structure, and include for example certain aromatic naphthas, C1 ⁇ 12alkyl-naphthalenes and -biphenyls, and benzyl alkylbenzenes.
• the solvents may also contain certain additives specifically intended to alter or control the final properties of the fluid, as for example viscosity control agents, vapour pressure control agents, freezing point depressants, odor masking agents and anti-oxidants.
• the chromogen used in the present invention is usually an aromatic compound containing a double bond system which is converted to a more highly polarised conjugated and coloured form when reacted with an acidic sensitizing material.
• a particularly preferred class of chromogens include compounds of the phthalide type, for instance crystal violet lactone which is 3,3-bis(p-dimethylaminophenyl)-6-dimethyl-aminonaphthalide, and malachite green lactone which is 3,3-bis(p-dimethylaminophenyl)phthalide.
• phthalide-derived chromogenic materials include 3,3-bis(p-di-propylaminophenyl)phthalide, 3,3-bis(p-methylaminophenyl)phthalide, 3-(phenyl)-3-(indole-3-yl)-phthalides such as 3-(p-dimethylaminophenyl)-3-(1,2-dimethylindol-3-yl)phthalide, 3,3-bis(methylindol-3-yl)-phthalides such as 3,3-bis(1,2-dimethylindol-3-yl)phthalide, 3-(phenyl)-3-(heterocyclic-substituted) phthalides such as 3-(p-dimethylaminophenyl )-3-(1-methylpyrrol-2-yl )-6-dimethylaminophthalide indole and carbazole substituted phthalides such as 3,3-bis(1,2-dimethylindol-3-yl)-5 - dimethyl
• chromogens useful in the practice of this invention include indole-substituted pyromellitides, for instance 3,5-bis-(p-diethylaminophenyl) - 3,5 - bis - (1,2 - di-methylindol - 3 -yl) pyromellitide, 3,7-bis-(p-diethylaminophenyl)-3,7-bis-(1,2-dimethylindole-3-yl)pyromellitide, 3,3,7,7-tetrakis-(1,2-dimethylindol-3-yl)-pyromellitide and 3,3,5,5-tetrakis-(1,2-dimethylindol-3-yl)pyromellitide; and leucauramines and substituted leucauramines such as for instance p-xylyl leucauramine and phenyl-leucauramine.
• orthohydroxybenzoacetophenone 2,4- bis(p-(p-dimethylaminophenylazo)aniline)-6-hydroxyl-sym-triazine, N,3,3-trimethylindolinobenzospiropyrans, and N,3,3-trimethylindolinobenzospiropyrans, and N,3,3-trimethylindolino-beta-naphthospiropyranes.
• An auxiliary colouring agent can be employed with the above chromogens to provide fade resistance where fading is a problem.
• Many phthalide compounds such as crystal violet lactone for example, are characterised by rapid colour development with a normal tendency to fade during the course of time.
• One suitable auxiliary coloring agent is benzoyl leuco methylene blue which oxidizes when released on the paper to slowly form a permanent blue colour.
• the combination of a phthalide chromogen and such a colourless oxidizable auxiliary colouring agent provides a composition having both rapid colour development and fade resistance.
• the invention also relates to a mark-recording system, preferably a carbonless copying paper two-sheet system, which makes use of the improved solvent.
• This system can be prepared according to well known conventional procedures. Descriptions of methods for preparing both the dye-carrying paper and clay-coating receiving paper are to be found in the literature.
• a preferred embodiment of this invention comprises a two-sheet system wherein the acid clay is carried by one sheet and a marking fluid comprising a chromogen and solvent is carried by a second sheet
• the invention is not limited to such systems alone.
• the only essential requirement is that the chromogen and the acid clay be maintained in a separate or unreactive condition until pressure is applied to the system and that upon the application of pressure the chromogen and acid clay are brought into reactive contact.
• the chromogen and acid clay present in a dry and unreactive state on a common carrier and to have the solvent alone carried on a separate sheet whereupon the application of pressure would release the solvent into the chromogen-acidic material mixture and promote localised reaction and colour development.
• a preferred aspect of the invention concerns primary solvents which comprise a mixture of 20% to 50% wt of the hydrocarbon compound and 80% to 50% wt of the ether compound.
• the primary solvents of the invention are used in combination with a secondary solvent in a weight ratio primary : secondary solvent ranging from about 40:60 to about 70:30. In a more preferred aspect the ratio primary : secondary solvent is from about 50:50 to 60:40.
• Colour formers which are particularly useful according to the invention for blue and black print using clay, resin and zinc salicylate developer systems are the following colour formers from Ciba-Geigy:
• Black prints are obtained with more complex colour former recipes of 3 (few formulations) up to 8 colour formers, with most of the formulations based on 5 to 6 colour formers.
• the colour former mix is used at about 0.5% to 10% wt in the solvent mixture.
• any particular colour former formulation is also based on shade, print intensity, light fastness as well as for some on the material used to build the capsule wall. Such choice is also influenced by the colour former cost.
• Dissolution tests were carried out by the following procedure: in a 50 ml beaker are placed 14.55 g of a primary solvent which can be an aromatic solvent, e.g. a partially hydrogenated terphenyl, or a combination of 5% up to 80% by weight of an aromatic solvent with as balance an aromatic ether.
• a primary solvent which can be an aromatic solvent, e.g. a partially hydrogenated terphenyl, or a combination of 5% up to 80% by weight of an aromatic solvent with as balance an aromatic ether.
• the colour former is added to the cold solvent or solvent blend with continous stirring.
• the mixture is then heated to 120°C while continuing the stirring until the colour former is completely dissolved.
• 9 g of cold kerosene are added under stirring. (On a weight basis this represents a 60/40 primary solvent/diluent blend).
• the solution is heated again to 120°C and this temperature is further held for 15 minutes. After such time the solution is allowed to cool to room temperature without stirring.
• the "Appearance” mentioned in the test results hereafter is a visual assessment of the amount of precipitate formed after 24 hours after the dissolution process.
• the scale is from 0 to 10. When no precipitate has appeared after 24 hours a "0" value is quoted for appearance, when all the colour former has precipitated a rating "10" is given.
• the validity of this test and its reproducibility have been tested by repeating some of the tests and a difference in rating of 1 to 2 units has been noticed.
• the test was conducted batchwise on a large number of samples of different structures/composition in order to reduce errors and to include "internal standards".
• Ciba-Geigy colour formers used, together with the chemical class to which they belong are given below.
• Pergascript Yellow I-3R Qinazoline compound Pergascript Orange I-5R Aminofluorane compound Pergascript Red I-6B Bis-indolyl phthalide compound
• Pergascript Blue I-2RN Crystal violet lactone Pergascript Blue I-2G Azaphthalide compound
• Pergascript Blue S-RB Bis-aryl carbazoyl methane compound
• Pergascript Blue S-4G Benzoyl leuco methylene blue (BLMB)
• Table 1 hereafter shows the appearance of colour former solutions prepared using partially hydrogenated terphenyl as primary solvent and the pure colour formers at 2 and 4% by weight, and using kerosene as secondary solvent at a weight ratio primary:secondary solvent of 60:40.
• Tables 2 to 7 show the appearance of various colour former solutions prepared using as primary solvent different aromatic solvent/ether solvent combinations, and as secondary solvent kerosene, in a weight ratio primary : secondary solvent of 60:40.
• the colour former is used at a concentration of 4% wt and/or 2% wt.
• TABLE 1 Appearance of solutions of pure colour formers in a primary solvent comprising partially (40%) hydrogenated terphenyl only. (Comparative data).

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Citations (5)

• 1990
  • 1990-11-20 EP EP90870216A patent/EP0486745A1/de not_active Withdrawn

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